A multitude of test systems and specialized time measurement devices have been developed to test the functional capabilities and reliability of integrated circuit products. One example of a time measurement device can be found in U.S. Pat. No. 6,091,671 (Kattan), which discloses a Time Interval Analyzer (TIA) for measuring time intervals between events in an input signal. Such patent is incorporated herein by reference for all purposes.
In accordance with the time measurement technology disclosed in U.S. Pat. No. 6,091,671, an input signal is received by front-end comparators, whereby a corresponding timing signal is generated. This timing signal is subsequently relayed to an interpolator-based measurement section at a fundamental data rate, which may typically be up to a maximum rate of about 3–4 Gbits/s.
Newly developed integrated circuit products employ rapidly increasing signal frequency levels that approach and sometimes exceed the maximum fundamental data rate of such conventional time interval analyzers. Since a large percentage of TIA test systems operate at such high speeds, it is a concern that various components of a TIA operating at such levels require very careful design and utilize expensive components that are often difficult to procure. Furthermore, such TIA components may be more sensitive to manufacturing variability and defects than components designed for operation at lower speeds.
Another concern related to conventional TIA devices is that as the signal frequency levels of TIA input signals increase, the relative accuracy of measurements obtained by the TIA can significantly decrease. This is due in part to the fact that transmitting shorter pulse widths through multiple stages of logic and/or connecting cables degrades signal accuracy.
Signal frequency levels are increasing at a greater rate than the development of new technological components fast enough to allow direct measurement of ultra high frequency signals, such as on the order of 10 Gbits/s (approximately 3× limit of currently measurable speed). Thus, it is desirable to provide features for improving the measurement of such signals beyond the current state of the art. More particularly, time measurement technology is desired with functionality to accurately measure signals with frequency levels that are at least a half an order of magnitude (i.e., three times) greater than the maximum data rate of conventional time measurement systems.
Time measurement features in accordance with the presently disclosed technology are configured to split an input signal into separate event streams, with each respective event stream having a lower fundamental data rate yet carefully maintained accuracy levels, thus allowing the measurement of such input signals even though their original data rate may otherwise be too high.